FIELD OF THE INVENTION
The present invention relates to a method for producing an electronic component, in particular a SAW component operating with surface acoustic waves. The component has electrically conductive structures, disposed on a surface of a substrate, and an encapsulation applied on the substrate and sealing the conductive structures. At least the conductive structures are covered with a protective layer.
An earlier, commonly owned application Ser. No. 08/743,540, filed Nov. 4, 1996, now U.S. Pat. No. 5,831,369 (see international published application WO 95/30276) describes an encapsulation for electronic components--particularly SAW components--with a cap that seals component structures on a substrate. The cap is formed by a cover which is provided on the substrate and has cutouts accommodating the component structures in regions thereof. The primary purpose of the cap cover is to protect the component structures, which in the case of SAW components, are essentially composed of electrically conductive structures on a piezoelectric substrate, against environmental influences as far as possible. This applies in particular to the encapsulation materials disclosed in the above application. It has been found that protection is not provided against gas diffusions, that is to say primarily against water vapor diffusion, or against attacks by specific chemical substances. In the context of some materials, the encapsulation behaves virtually as if it were not there with respect to water vapor diffusion. In consequence, the frequency stability of the components can no longer be guaranteed both as a result of water vapor diffusion and as a result of chemical substances.
U.S. Pat. No. 4,617,487 to Sone et al. discloses an SAW component having a cap which is, for example, nickel-coated for the purpose of sealing and corrosion resistance, and which is seated in a hermetically sealed manner on a mounting plate for the SAW component. In that case, the entire active component structure is covered by a closed tantalum pentoxide or silicon nitride layer for protection against possible short circuits caused by elements fragmenting off, for example the nickel coating.